Fluid displacement systems with which the present invention is concerned are at times referred to as "passive" or "self-pumping pump system", "geyser-type pump systems", "heat" or "thermal actuated pump systems" etc. However, heretofore prior art systems in the related field typically comprise mechanical or electromechanical components such as pumping means, valves etc, which require control means and an energy source and which in many cases are suitable only for liquids and are not suitable for handling gas or vapor or a combination of gas or vapor and liquid. Furthermore, such mechanical components require periodical maintenance and replacing due to wear.
The following is a brief description of some prior art references which are in the related field and from which the present invention is clearly distinguishable:
U.S. Pat. No. 4,573,525 discloses a heat actuated heat exchange system comprising a conduit in a primary heating zone, a boiler in a second heating zone and an accumulator in a third heating zone, connected by another conduit zone to a condenser two check valves and a heat rejector, forming together a sealed device containing a condensable coolant.
The drawbacks of this patent are that it requires heat as an energy source which heat must be effected to three different stages of the device. Furthermore, the system requires two check valves for ensuring fluid flow in desired direction only. It is also apparent that the system will not function unless it is sealed.
U.S. Pat. No. 4,552,208 discloses an apparatus for circulating a heat transfer liquid from a heat collector such as a solar collector panel, to a heat exchanger such as heat storage means. However, this device is level-dependant and will operate only if the heat exchanger is located at a level below that of the heat collector.
U.S. Pat. No. 4,478,211 is a "geyser-type" heat exchanger which depends on the production of differences in liquid levels so as to create sufficient hydrostatic pressure imbalance for promoting flow of a heated liquid.
The liquid displacing forces in the '208 and '211 are limited by the elevation differences between the inlet and the outlet of the heated liquid connecting tube.
The heat exchange system disclosed in U.S. Pat. No. 3,929,305 comprises a reservoir for a coolant liquid conveyed via a conduit through a heating zone and a check valve for preventing a reverse flow in the conduit. Apart from the fact that this system requires a check valve, it is also sensitive to the heat applied to the system, and the cycle under which the device operates resembles the generative cycles of Sterling or Ericson engines.
U.S. Pat. No. 2,738,928 discloses a sealed heat exchange system having an internal pumping mechanism consisting of a heat separator in which dimensions of the associated components are critical in order to keep the system in balance. Moreover, the system relies on a connecting tube extending between a heating vessel and a distribution, said connecting tube being of a capillary caliber in order to ensure liquid level rise within the tube, regardless of any other factors. This arrangement ensures that the opening of the connecting tube is sealed within the heating vessel is always sealed by the capillary rise of liquid within the tube, owing to the surface tension force acting between the tube's lowermost edge and the liquid within the heating vessel. For that reason, the opening of the connecting tube is typically flared i.e, bell-like shaped. It thus appears that the system according to that patent is operable only with liquids as a working fluid, and not with gases.
Other references which are in the field of the invention are U.S. Pat. Nos. 3,484,045; 4,177,019; 4,197,060; 4,246,890; 4,270,521; 4,366,853; 4,467,862; 4,611,654; and 4,676,225 each of which shares one or more of the drawbacks disclosed in the above disclosed patents and are thus considered to be distinguishable.
It is an object of the present invention to provide a new and improved, self activated fluid displacement system, devoid of any mechanical or electromechanical components and in which the above-referred to drawbacks are substantially reduced or overcome.